1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus both having pressure chambers and piezoelectric elements. The pressure chambers communicate with nozzle openings, and the piezoelectric elements each have a piezoelectric layer and electrodes for energizing the piezoelectric layer and can change the pressure in the pressure chambers. The invention also relates to such a piezoelectric element.
2. Related Art
A typical form of piezoelectric element is a piezoelectric material having an electromechanical conversion function, such as a piezoelectric layer (a piezoelectric film) composed of a crystalline piezoelectric material and sandwiched between two electrodes. This type of piezoelectric element can be used in liquid ejecting heads as flexural-vibration-based actuators. Typical examples of liquid ejecting heads are ink jet recording heads. An ink jet recording head has nozzle openings for ejecting ink droplets, and these nozzle openings communicate with pressure chambers. These pressure chambers share a diaphragm as one of their components. Piezoelectric elements vibrate to deform the diaphragm, and the deformed diaphragm pressurizes the ink contained in appropriate pressure chambers to eject it from appropriate nozzle openings in the form of droplets.
Piezoelectric materials used to form this type of piezoelectric layer should have good piezoelectric properties. A typical example is lead zirconate titanate (PZT) (see JP-A-2001-223404). Recently, however, environment-conscious people have called for low-lead piezoelectric materials. Some examples of lead-free piezoelectric materials are KNN-based ones, which contain potassium (K), sodium (Na), and niobium (Nb). KNN-based materials have a high Curie point and excellent electric properties.
Unfortunately, however, KNN-based piezoelectric materials allow electricity to leak therethrough and are poor insulators. This type of problem is not unique to ink jet recording heads and other kinds of liquid ejecting heads; similar problems may be encountered with piezoelectric elements for other devices.